1. Field of the Invention
The present invention relates generally to liquid pumping and collecting apparatuses, and more particularly to a bladder pump for pumping underground liquid, such as groundwater samples, from small diameter wells. It should be noted, however, that the invention is also applicable and adaptable in various other applications that will occur to one skilled in the art from the disclosure herein.
2. Description of the Prior Art
Recent increases in public concern for the environment have resulted in various government-imposed environmental regulations with regard to groundwater quality and land-site cleanup projects. Among such regulations are requirements relating to the monitoring and sampling of water quality of aquifers as sources of drinking water. In response to these requirements, water quality analytic capabilities have been improved and water-sampling equipment has been developed. However, presently most sampling using bladder pumps employ permanently installed dedicated pumps in monitoring wells. Current portable equipment for the groundwater sampling is relatively heavy, bulky, and thus difficult to transport from one monitoring site to another.
One of the preferred types of pumps for groundwater sampling or other pumping applications is a submersible, fluid-actuated pump wherein the actuating fluid is preferably a gas such as compressed air. A flexible bladder member in this type of pump separates and isolates the interior of the pump into two chambers: a liquid chamber that contains the sample fluid and is in communication with both the pump inlet and outlet, and a gas chamber surrounding the first chamber, and connected to a source of the actuating gas, with the bladder disposed therebetween. The pumped liquid is conveyed through the pump by alternately pressurizing and venting or relieving the pressure in the gas chamber to contract and relax the bladder member, thus alternately decreasing and increasing the volume of the liquid chamber. The pumped liquid is drawn into the liquid chamber during such increases in volume under the influence of the natural hydrostatic head of the groundwater or other pumped liquids and is discharged through the pump outlet during such decreases in volume, thereby conveying the pumped liquid through the pump.
The conventional bladder pumps have proven to be not very efficient, however, in obtaining consistent, non-contaminated water samples that are accurately representative of the water system from which the sample is taken. The inadequacies of previous sampling equipment stem largely from such causes as cross-contamination between sampling sites, ineffective and inconsistent field cleaning methods, contamination due to equipment handling, and inconsistent well depth sampling. In addition to presenting sample quality problems, much of the previous equipment has been heavy and bulky and thus difficult to transport from one monitoring site to another.
Moreover, conventional bladder pumps for groundwater sampling have proved to be complicated to operate, relatively expensive, and impractical for sampling at remote locations where site access is severely limited. The need therefore exists for more efficient and easy to operate liquid sampling bladder pumps.
The present invention alleviates the drawbacks of the prior art. The present invention provides a pump for a wide variety of applications, including, but not limited to, groundwater quality applications, withdrawing and collecting contaminated groundwater or other subterranean liquids from a landfill-site having a plurality of in-ground wells. The novel pump may be built with a small outside diameter, such as 1.315xe2x80x3, and is adapted to sample temporarily and/or permanently installed small diameter monitoring wells. The bladder pump of the present invention is particularly effective for conducting xe2x80x9clow-flow samplingxe2x80x9d from monitoring wells where minimal purging is undertaken prior to sample collection. Please note that low-flow refers to the velocity with which water enters pump intake and that is imparted to the formation pore water in the immediate vicinity of the well screen.
The preferred liquid sampling pump is an air-operated, gas-displacement bladder pump having a generally tubular casing submersible in the in-ground well. The pump body includes a liquid inlet with an inlet check valve for allowing one-way fluid flow from the in-ground well into the housing interior, and a liquid outlet with an outlet check valve allowing one-way fluid flow from the pump body interior to the discharge collection equipment. The liquid sampling pump further includes a top cap attached to an upper end of the casing and provided with a fluid communication port and a liquid outlet port, a top bladder mandrel secured to the top cap, a mandrel sealing member disposed in a lower end of the casing and defining an inlet chamber within the lower end thereof, a bottom bladder mandrel secured to the mandrel sealing member, and a flexible bladder extending between the top bladder mandrel and the bottom bladder mandrel and defining a liquid chamber for receiving the liquid therein and a fluid chamber for receiving a fluid under pressure therein that surrounds the liquid chamber, with the bladder disposed therebetween. The fluid chamber is in fluid communication with the fluid communication port that is connected to a source of the actuating gas, while the liquid chamber is in one-way fluid communication with the liquid inlet and the liquid outlet port.
The sample fluid is conveyed through the pump by alternately pressurizing and venting or relieving the pressure in the second chamber to contract and relax the bladder member, thus alternately decreasing and increasing the volume of the first chamber. Sample liquid is drawn into the liquid chamber during such increases in volume under the influence of the natural hydrostatic head of the groundwater and is discharged through the liquid outlet port during such decreases in volume, thereby conveying the sample liquid through the pump. The components of the pump are preferably composed of low-cost, lightweight synthetic materials that are non-corrosive and do not otherwise affect the chemical composition of the sampled fluid.
Additional advantages and features of the present invention will become apparent from the following description and the appended claims taken in conjunction with the accompanying drawings.